Device for catheter sheath retraction

ABSTRACT

A device for moving an elongate member relative to an elongate body through which it extends, the device including a housing, a mover, and a pre-mover. The housing is connectable to the elongate body. The mover is associated with the housing and is connectable to the elongate member for moving the elongate member relative to the housing. The pre-mover is associated with the housing and is connectable to the elongate member for adjusting the elongate member in preparation for moving the elongate member with the mover.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.13/958,460, filed Aug. 2, 2013, now U.S. Pat. No. 9,421,115, which is acontinuation of U.S. patent application Ser. No. 12/668,613, filed Feb.19, 2010, now U.S. Pat. No. 8,500,789, filed as a U.S. national stageapplication under 35 USC § 371 of International Application No.PCT/EP2008/059040, filed Jul. 10, 2008, claiming priority to GreatBritain Patent Application No. 0713497.6, filed Jul. 11, 2007, each ofwhich is incorporated by reference in its entirety into thisapplication.

FIELD OF THE INVENTION

The present invention relates to a device for moving an elongate memberrelative to an elongate body through which it at least partiallyextends, to a device for moving an elongate member by a predetermineddistance relative to an elongate body through which it at leastpartially extends, thereby to release a stent at the distal end of theelongate body, and to surgical apparatus including such devices. Morespecifically, the invention is concerned with medical transluminalcatheters such as those used to deliver a stent to a vascular treatmentlocation, and the devices by which a medical practitioner operates suchcatheters from a location external of the patient.

BACKGROUND OF THE INVENTION

It has long been desirable to reduce the degree of trauma caused by, andattendant risks associated with, surgical procedures. In order tofurther this aim, there have been a large number of technical advancesin recent times to enable various surgical procedures to be carried outusing minimally invasive techniques.

One particular form of treatment to have benefited from advances inminimally invasive surgical procedures is the treatment ofcardiovascular diseases. Whereas in the past it would have beennecessary to conduct an open procedure in order to access the heart or aportion of the venous system, minimally invasive techniques have nowbeen developed in which a catheter-based piece of surgical equipment canbe deployed to a treatment location within a patient's cardiovascularsystem from a remote location external to the patient. Specifically, anelongate endoluminal catheter is inserted percutaneously through anincision in a patient's skin and is then advanced transluminally throughthe patient's vasculature from the incision location to a treatmentlocation. A control device, mounted at the proximal end of the surgicalcatheter, is used to control the equipment mounted at the distal end ofthe surgical catheter, which has been advanced to the treatmentlocation, from a remote location external to the patient's body.

In one particular technique, a stent is mounted on a distal end portionof the surgical catheter in a reduced-diameter configuration. Thesurgical catheter includes a retractable sheath which extends along atleast the distal portion of the catheter to enclose the stent and toretain the stent in the reduced-diameter configuration. When thecatheter distal portion has been advanced to the treatment location, thesheath is retracted to expose the stent. The stent is then caused toexpand to an increased-diameter configuration at the treatment location,so that its abluminal surface engages the vessel inner wall, andthereafter serves to maintain an open fluid passageway through thevascular treatment location. The surgical catheter is then retrievedfrom the patient, leaving the stent in place. Preferably the stent is aso-called self-expanding stent, typically manufactured from a shapememory alloy, such as Nitinol, and being configured to expand from thereduced diameter configuration to the increased-diameter configurationdue to the memorized molecular configuration of the alloy at bodytemperature. When the sheath is retracted, such a stent therefore adoptsthe increased-diameter configuration without further intervention by themedical practitioner. Balloon-expandable stents, and otherconfigurations, are also known, however, which require intervention bythe medical practitioner to cause the stent to expand from thereduced-diameter configuration to the increased-diameter configuration.

In order to be insertable through the tortuous vasculature of a patient,from the mc1s10n location to the treatment site, a surgical cathetermust be flexible transverse to its longitudinal axis. This allows thecatheter to follow the narrow and twisting passageways through thepatient's venous system. On the other hand, such catheters must berelatively incompressible in the lengthwise direction, so as tofacilitate catheter advancement by providing a driving force to guidethe catheter into the vasculature from the proximal end, and so as toresist compression during retraction of the catheter sheath when a stentis to be released. For this purpose, it is not uncommon to provide ameans of reinforcing the inner tubular portion of the surgical catheter,such as by providing a coil spring along the length thereof from theproximal end to the distal portion. Such a coil spring is closely wound,with adjacent turns of the coil being substantially in contact with oneanother, to resist compressive forces but provides the requisite degreeof flexibility transverse to the coil's central axis. A so-called stentpusher may be provided at the coil distal end, configured to engage thestent and to prevent proximal displacement of the stent when a retainingsheath is withdrawn for stent release.

The sheath provided to restrain the stent in the reduced diameterconfiguration may be provided so as to extend along the entire length ofthe surgical catheter, from the proximal end to the distal tip. On theother hand, the sheath need only be provided in a region at the distalportion of the catheter, sufficient to enclose the stent along itslength, and being retractable to fully expose the stent. In either case,a sheath retraction wire may be provided by which to withdraw the sheathproximally along the catheter, thereby exposing the stent at thecatheter distal end portion. Typically, as noted, the stent will beself-expanding, so as to place the sheath under a circumferentialpre-tension. In order to allow the sheath to slide over the catheter,the catheter and sheath are usually constructed from low-frictionmaterials, and provided with a lubricant or lubricious surface treatmentthere-between.

At the proximal end of the surgical catheter, a device is provided forretracting the sheath over the catheter. Typically, such a deviceincludes a housing by which a medical practitioner can grip the device,and to which the catheter is rigidly connected. In particular, anyreinforcing member, such as a coil spring, is attached to the devicedistal end by a hub, by which to hold the reinforcing member in place. Aretraction wire is typically provided, attached at its distal end to oneend of the catheter sheath, by which to withdraw the sheath. Typically,the retraction wire extends from the connection point with the sheath,into and through a lumen inside the catheter, to extend from theproximal end of the catheter inside the device housing. An actuator isprovided, operable by the medical practitioner using the device, bywhich the sheath wire is retracted to withdraw the sheath and expose thedistal portion of the catheter. In alternative configurations, aretraction wire is not necessitated, and the sheath may be connecteddirectly to a portion of the actuator mechanism within the housing. Inmost applications, the catheter sheath is configured to be withdrawnproximally along the catheter, but distal withdrawal is not impossible.The reinforcing member serves to resist compression due to the tensilestresses in the catheter sheath and retraction wire. The resultingcompressive stresses are transferred from the reinforcing member to thedevice via the connection hub by which they are joined.

WO 02/087470 A1 discloses a sheath refraction device for proximallywithdrawing a catheter sheath. The sheath is in the form of an outertube 16 connected at its proximal end to a slider 24 in the devicehousing. As the slider 24 is proximally withdrawn, the sheath isretracted. The retraction device in WO 02/087470 A1 provides twoactuation mechanisms by which the sheath may be withdrawn. The first isto provide a finger engagement portion (a button) on the slider 24, bywhich the slider and the connected outer tube 16 may be directlyproximally withdrawn by refracting the slider along slider tracksprovided. The second mechanism by which the sheath may be withdrawn isactuated by a finger trigger 34. A pull wire 30 extends proximally fromthe slider 24 to a take-up reel 32. The take-up reel is connected to atoothed gear 35, which engages with ratchet teeth 36 of the trigger 34.When the trigger is depressed, the ratchet teeth rotate the toothed gear35 so as to wind the pull wire 30 on the take-up reel 32, therebyretracting the slider and connected sheath proximally in the housing.Because the teeth 36 are ratchet teeth, the take-up reel may only berotated in one direction by successive pulls of the trigger. The lengthof a retraction stroke possible with the device of WO 02/087470 A1 isrestricted by the length of the track provided for the slider 24 in thehousing.

A similar device is disclosed in WO 2007/022395. In this device, acatheter outer sheath 262 is rigidly attached to a slider block 624 inthe device housing. A belt 670 is provided, connected to the sliderblock 624 and passing around a proximal idle pulley 638 to be connectedat its other end to a take-up pulley 656. Take-up pulley 656 may berotated by an operator via a knob 640, 650, in order to wind the belt670 onto the reel 656. As the belt is wound onto the reel, the hub 624is retracted so as to withdraw the outer sheath 262. As the belt iswound onto the take-up pulley 656, the winding diameter of the pulleyincreases, thereby reducing the mechanical advantage afforded,simultaneously increasing the degree of retraction for a given rotationof the knobs 640, 650. A lock 646 may be provided so as to inhibitrotation of the knobs 640, 650 during shipping, although explanation ofthe operation of this lock is not given. The length of a retractionstroke of the device is again limited by the length of the trackprovided for sliding the proximal hub 624 within the device housing.

Several sheath retraction devices are disclosed in WO 2005/039448 A1. Inthe first illustrated embodiment of FIGS. 1 to 5, a wire 160 isprovided, connected to the outer tube (sheath) 130. The wire isconnected to a cam 190 in the device housing. The cam is coupled to athumbwheel 180, which may be rotated by a medical practitioner whenusing the device. Rotation of the thumbwheel 180 causes the wire 160 tobe wound onto the surface 192 of the cam 190 so as to withdraw the outertube 130 proximally with respect to the catheter inner tube 140. Sincethe radius of the cam 190 increases around the cam's surface 192, themechanical advantage provided for retracting the outer tube 130decreases as the wheel 180 rotates, with the degree of retraction for agiven amount of rotation of the thumbwheel 180 correspondinglyincreasing as the thumbwheel 180 rotates. The device of WO 2005/039448is configured to achieve only a single rotation of the thumbwheel 180,thereby limiting the retraction stroke to a distance equal to thecircumference of the cam outer surface 192.

For minimally invasive surgical procedures utilizing a catheter, as withany surgical procedure, hygiene is of paramount importance. Regardlessof the level of trauma caused by the surgical operation, the risks ofinfection must be minimized or neutralised, to ensure and aid apatient's recovery. For this reason, surgical catheter devices areusually provided with a control device already attached to thecatheter's proximal end, and, in the case of a stent delivery catheter,with the stent already loaded in the catheter distal end. The surgicalapparatus is typically packaged in sterile packaging, ready for use whenfirst exposed from the packaging.

Because a surgical catheter is typically several times longer than theassociated control device, the catheter is normally packaged in arolled, folded or bent configuration, rather than in a fully elongated,straight configuration. This is enabled by the inherent flexibility ofsuch catheters. In order to use the surgical apparatus, the catheter isstraightened for insertion transluminally into a patient, and is thenguided to the treatment site within a patient's vasculature. Typically,a guide-wire is provided, along which the catheter is run, to bring thedistal end of the catheter to the treatment location.

Both when folding and unfolding the catheter for packaging anddistribution purposes, and also when running the catheter along aguide-wire to follow a tortuous passage way, localized relative motionnecessarily occurs between the catheter and the sheath. In particular,the sheath is necessary relatively inextensible in the lengthwise axialdirection, to enable controlled withdrawal in use. The catheter materialis typically moderately elastic, so as to provide the necessary lateralflexibility, with rigidity provided by a coil spring or otherreinforcing support member as described above. As the catheter bends andflexes, localized movement between the catheter and sheath can thusoccur. So that this will not result in accidental premature retractionof the sheath, the sheath distal end may be formed to extend over theend of the catheter to form an atraumatic distal tip. In other knowncatheters, an atraumatic tip may simply be provided on the distal end ofthe catheter. An element of slack or flexibility is also typicallyprovided in the sheath retraction wire, which is itself substantiallyinextensible, so as to accommodate relative motion of the sheathproximal end with respect of the catheter.

The overall effect of the tolerances provided to allow such flexibilityand relative motion means that when the operator comes to retract thesheath, the initial stages of sheath retraction may not deliver acontrolled or expected degree of motion in the sheath, as the slack istaken up. In particular, at the initial stages of stent deployment, itis essential to have full control of the positioning and placement ofthe stent at the distal end of the surgical catheter device, to preventaccidental movement of the stent relative to the treatment site, whichcould result in an unintentional patient trauma.

There is also typically some inherent lengthwise compressive flexibilityin the catheter, and some lengthwise tensile flexibility in the sheath,upon initial delivery to the treatment site, before any residualcompressibility or extensibility can be taken up by proximal lengthwisetensioning of the sheath wire to place the catheter under compressionalong the catheter length. This initial catheter compression can produceundesirable preliminary motion at the catheter distal end as the sheathretraction device is first actuated.

Whilst prior art devices including two or more separate retractionmechanisms for delivering different mechanical advantages have beenprovided, so as to achieve slow initial sheath withdrawal for accurateplacement of the stent distal end and fast subsequent sheath withdrawalfor quickly releasing the stent when placed, no device has yet beenproduced to specifically account for the inherent residual tolerancesand material resilience of the surgical catheter construction. It wouldtherefore be desirable to provide a sheath withdrawal device constructedand arranged to accommodate specifically such residual tolerances andthe material resilience of the surgical catheter construction.

It would also be desirable to provide indication to the user of suchdevices of when the sheath has been fully retracted, to ensure properand accurate stent release and to indicate when the catheter may beretracted from the patient.

WO 20061104143 A1 discloses a body organ expansion instrument 1 having atubular member 5 capable of sliding in a proximal direction at thedistal end of a distal tube 2. A pulling wire 6 is attached at theproximal end to a winding shaft portion 63 which retracts the wire 6 bywinding wire 6 thereon. A linear member 71 is also provided to be woundonto shaft portion 63 also. The linear member is fed out from a bobbin73, around which it is initially wound, as the linear member 71 is woundonto shaft portion 63. When linear member 71 is all fed out, the bobbin73 is nonrotatable, thereby making rotational roller 61, which winds theshaft portion 63 to retract wire 6, incapable of further rotating. Theend 71 a of the linear member 71 is inserted into a slit 72 to be heldon the shaft portion 63. The shaft portion 63 is, however, provided onlywith a single slit 72, and the length of linear member 71 must thereforebe made in accordance with the length of the specific stent to be heldby tubular member 5 at the distal end of distal tube 2.

It would be desirable to provide means whereby the same device, ordevices having substantially identical construction, can be adapted forretracting the sheath by amounts corresponding to different lengths ofstents to be released, and to provide indication of full and propersheath retraction appropriate to the length of each stent beingreleased.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda device for moving an elongate member relative to an elongate bodythrough which it at least partially extends, the device comprising ahousing connectable to the elongate body; a mover associated with thehousing and connectable to the elongate member for moving the elongatemember relative to the housing and relative to a connected elongatebody; and a pre-mover for adjusting an elongate member connected to themover relative to an elongate body connected to the housing inpreparation for moving the elongate member with the mover.

In preferred embodiments, the pre-mover resists movement of the elongatemember by the mover prior to adjusting the elongate member.

In further preferred embodiments, the pre-mover is configured foradjusting the elongate member relative to the elongate body to reduceslack between the elongate member and the elongate body to ensure directsubsequent relative movement therebetween by the mover.

In yet further preferred embodiments, the pre-mover is configured toadjust the mover relative to the housing so as to relatively adjust theelongate member and the elongate body respectively connected thereto.

In even further preferred embodiments, the pre-mover is configured toeffect a predetermined relative adjustment between the elongate memberand the elongate body.

In yet even further preferred embodiments, the pre-mover is configuredto become inoperable following adjustment of the elongate member.

In more preferred embodiments, the mover is operable to move theelongate member only in a first direction relative to the elongate body.

In yet more preferred embodiments, the device is configured for themover to move the elongate member towards the housing relative to theelongate body, which is fixedly connected to the housing.

In even more preferred embodiments, the device further comprises anaccumulator, by which the elongate member is connectable to the moverand a portion of the elongate member is formed as an accumulation in thehousing.

In yet even more preferred embodiments, the device further comprises alimiter for limiting the extent of movement of the elongate memberrelative to the elongate body. In such embodiments, the limiter maycomprise a band of substantially inextensible material which isconnected at one end to, and is wound on, a spool which is mounted tothe housing, the band being connected at the other end to a windingmember of the mover onto which the band is wound from the spool as themover moves the elongate member, thereby permitting movement of themover until the band is fully unwound from the spool and thereafterpreventing further movement of the elongate member by the mover.

In still further preferred embodiments, the elongate body comprises asurgical catheter configured for insertion into a bodily lumen, andwhich includes a sheath which surrounds at least a distal end portion ofthe catheter; the elongate member is a wire for moving the sheathrelative to the catheter; and the housing is connectable to a proximalend of the catheter.

In yet still further preferred embodiments, the mover comprises atake-up reel mounted to rotate relative to the housing onto which theelongate member is wound to effect movement thereof.

In still even further preferred embodiments, the mover includes anactuator by which a user of the device may actuate the mover to move theelongate member. In such embodiments, the actuator may include a triggerpivotally mounted to the housing to pivot between an extended positionand a depressed position and configured to rotate a trigger gear bywhich to actuate the mover. More preferably, the trigger may include aplanetary gear by which to rotate the trigger gear. Even morepreferably, the trigger gear is coupled to a drive shaft of the mover bya one-way clutch so as to enable the trigger gear to rotate the driveshaft when depressed towards the depressed position but preventing thetrigger gear from rotating the drive shaft when returned towards theextended position, the trigger being biased towards the extendedposition.

In still more preferred embodiments, the mover includes: a toothed gearmounted to rotate relative to the housing; and a leaf spring fixedlymounted to the housing and arranged so that one end thereof engages withthe teeth of the toothed gear at a non-radial angle of incidence to thegear, the leaf spring being resiliently flexible to disengage from thegear teeth and allow rotation of the toothed gear in one direction andto engage the gear teeth and substantially resist rotation of the gearin the other direction, so as to effect a ratchet arrangement to permitactuation of the mover to move the elongate member only in one directionrelative to the elongate body.

In yet still more preferred embodiments, the pre-mover includes a rackgear configured to engage initially with a pinion gear of the mover, sothat adjustment of the elongate member relative to the elongate body iseffected by actuation of the rack gear to rotate the pinion gear of themover.

In still even more preferred embodiments, the rack gear is mounted to aslider arm which is connected at one end to a button which is mounted toslide relative to the housing and is arranged to be actuated by a userto effect actuation of the rack gear.

In yet still even further embodiments, the housing forms a sealed unitin which the mover and pre-mover are mounted to be actuated by a user.In such embodiments, preferably the housing is sized and configured, andan actuator of the mover and of the pre-mover are arranged, so as tofacilitate operation of the device with a single hand by a user.

According to a second aspect of the present invention, there is provideda device for moving an elongate member by a predetermined distancerelative to an elongate body through which it at least partiallyextends, thereby to release a stent at the distal end of the elongatebody, the device comprising: a take-up reel onto which the elongatemember is wound when it is moved; and a limiter that is configured tolimit further rotation of the take-up reel after a length of theelongate member has been taken up on the reel to move the elongatemember said pre-determined distance, wherein the limiter comprises atethered line, which is configured to be progressively consumed when thetake-up reel is rotated until the tethered line anchors the take-up reelagainst further rotation, one end of the tethered line being providedwith a line connector by which it may be attached to a limiter reel onwhich it is to be taken up to be consumed, and wherein the limiter reelis provided with plural reel connectors to which the line connector maybe connected to attach the tethered line to the limiter reel.

In preferred embodiments, the line connector is a male connector and thereel connectors are female connectors into which the male connectors canbe connected. More preferably, the line connector is a ball or cylinderjoined onto the end of the tethered line. Yet more preferably, thetethered line has a total length, of which a consumable lengthcorresponding to the length of said elongate member to be taken up mayform all or a portion, the limiter being adjustable to set theconsumable length to correspond to the length of said elongate member tobe taken up prior to use of the device for effecting the predeterminedrelative movement between the elongate body and the elongate member,preferably during manufacture-and-assembly of the device.

According to a third aspect of the present invention, there is provideda device for moving an elongate member by a predetermined distancerelative to an elongate body through which it at least partiallyextends, thereby to release a stent at the distal end of the elongatebody, the device comprising: a take-up reel onto which the elongatemember is wound when it is moved; and a limiter that is configured tolimit further rotation of the take-up reel after a length of theelongate member has been taken up on the reel to move the elongatemember said pre-determined distance, wherein the limiter comprises atethered line, which is configured to be progressively consumed when thetake-up reel is rotated until the tethered line anchors the take-up reelagainst further rotation, wherein the tethered line to be consumed has aconsumable length corresponding to the length of said elongate member tobe taken up, and wherein (i) a plurality of tether lines are providedhaving different respective consumable lengths, from which the tetheredline to be consumed is selected having a consumable length whichcorresponds to the length of said elongate member to be taken up, or(ii) a tether line is provided having reference markings along itslength indicating different consumable lengths corresponding todifferent lengths of said elongate member which can be taken up, theconsumable length being set by the tether line being consumed, prior tomoving the elongate member, up to the reference marking which indicatesa remaining consumable length corresponding to the length of saidelongate member to be taken up.

Preferably, the tethered line is consumed by being taken up on a limiterreel. More preferably, the tethered line is carried on a tether spool,and is unspooled from the tether spool while being progressivelyconsumed during rotation of the take-up reel.

In further preferred embodiments, the elongate body is a catheter andthe elongate member IS a sheath refraction wire for proximallyretracting a sheath that surrounds the abluminal surface of the stent tobe released at the catheter distal end.

The present invention also provides a surgical apparatus including adevice as set forth above and having an elongate body connected to thehousing and an elongate member connected to the mover.

In preferred embodiments, the surgical apparatus further includes astent carried by the elongate body for delivery to a target site of apatient and releasable from the elongate body at the target site bymovement of the elongate member relative to the elongate body.Preferably, the stent is a self-expanding stent suitable to be implantedat a treatment location in a bodily lumen, and the device is configuredto effect a pre-movement adjustment of the elongate member relative tothe elongate body, said adjustment including a preliminary movement ofthe elongate member relative to the elongate body insufficient torelease any portion of said stent to an expanded diameter permittingcircumferential engagement with the inner wall of the bodily lumen atthe intended treatment location. More preferably, said preliminarymovement is insufficient to release any portion of said stent from theelongate body. Most preferably the stent is a self-expanding stent, andthe device is configured to effect a pre-movement adjustment of theelongate member relative to the elongate body, said adjustment includinga preliminary movement of the elongate member relative to the elongatebody insufficient to release any portion of the stent to an expandeddiameter of more than 110% of the stent unreleased diameter, preferably105% or less of the stent unreleased diameter.

According to a fourth aspect of the present invention, there is provideda stent delivery device, comprising: a housing connectable to anelongate body; a mover coupled to a housing and connected to an outersheath disposed over a stent compressed about a distal end of theelongate body; and a pre-mover associated with the housing having alocked position engaging the mover and an unlocked position in which themover is released, wherein movement of the pre-mover from the lockedposition to the unlocked position prepares the outer sheath fordeployment of the stent.

According to a fifth aspect of the present invention, there is provideda stent delivery device, comprising: a take-up reel onto which a sheathretraction line is wound when an outer sheath which surrounds acompressed stent at a distal portion of the delivery device isretracted; and a limiter which limits the length of the sheathretraction line which may be taken up on the reel so as to limitretraction of the outer sheath, wherein the limiter comprises a limiterreel and a tethered line which is progressively consumed by the limiterreel when the take-up reel is rotated and which anchors the take-up reelagainst further rotation when fully consumed, one end of the tetheredline being provided with a line connector attached to the limiter reel,and wherein the line connector is connected to one of plural reelconnectors disposed around the limiter reel.

According to a sixth aspect of the present invention, there is provideda stent delivery device, comprising: a take-up reel onto which a sheathretraction line is wound when an outer sheath which surrounds acompressed stent at a distal portion of the delivery device isretracted; and a limiter which limits the length of the sheathretraction line which may be taken up on the reel so as to limitretraction of the outer sheath, wherein the limiter comprises a limiterreel and a tethered line connected to the limiter reel, which isprogressively consumed by the limiter reel when the take-up reel isrotated, wherein the tethered line has a consumable length correspondingto the retraction limit of the outer sheath, and wherein (i) one or morefurther tether lines are provided having respective consumable lengthsdifferent from the length of the tethered line connected to the limiterreel, or (ii) the tether line connected to the limiter reel hasreference markings along its length indicating different availableconsumable lengths, the consumable length which corresponds to theretraction limit of the outer sheath being indicated by one saidreference marker.

Embodiments of the first and fourth aspects of the invention set forthabove are able to provide adjustment prior to bulk actuation of themover, ensuring that tolerances are accommodated and that motion betweenthe mover and housing translates directly into proportional motionbetween the elongate member and elongate body, thereby improving controlaccuracy with the device.

In particular for stent delivery catheter embodiments, unexpecteddeflection at the catheter tip as the sheath retractor is firstactivated can be reduced or eliminated.

Furthermore, an effective locking mechanism may be achieved, withcertain embodiments, to prevent premature or accidental actuation of themover.

Preferred embodiments are also able to accommodate different strokelength requirements, as the stroke length need not be restricted by thelength of the housing or its components.

Embodiments of the second, third, fifth and sixth aspects of theinvention set forth above can indicate to the user of the device, when astent at the elongate body distal end has been fully released,preventing premature catheter withdrawal or unnecessary further movementof the elongate member, and are readily adaptable to different lengthsof stent which the devices may be employed to release.

BRIEF DESCRIPTION OF THE DRAWINGS

To enable a better understanding of the present invention, and to showhow the same may be carried into effect, reference will now be made, byway of example only, to the accompanying drawings, in which: —

FIG. 1 shows an exploded perspective view of a catheter sheathretraction device as one embodiment of a device in accordance with thepresent invention, detailing the major internal and external componentparts of the device;

FIG. 2 shows a cross-sectional left-hand-side view of the cathetersheath retraction device of FIG. 1;

FIG. 3 shows a plan view of the main internal components forming thesheath retraction mechanism of the catheter sheath refraction device ofFIG. 1 and FIG. 2;

FIG. 4 shows a similar plan view of the components of FIG. 3, with theplanetary gear omitted, indicating how a trigger gear is connected tothe main shaft of the sheath retraction mechanism by virtue of a one-wayclutch;

FIG. 5 shows a left-hand-side view of the working components of theretraction mechanism of the catheter sheath retraction device of FIGS. 1to 4;

FIG. 6 shows a right-hand-side view of the retraction mechanism of thecatheter sheath retraction device of FIGS. 1 to 5;

FIG. 7 shows a perspective exploded view of the components of FIGS. 5and 6;

FIG. 8 shows a detailed view of the trigger actuator components of thecatheter sheath retraction device of FIGS. 1 to 7;

FIG. 9 shows a view of the components of a pre-mover assembly of thecatheter sheath retraction device of FIGS. 1 to 8; and

FIG. 10 shows an exploded perspective view of the main rotational shaftat the center of the catheter shaft retraction device of FIGS. 1 to 9,and the rotary components to be mounted thereto.

DETAILED DESCRIPTION

The following detailed description is directed to a specific example ofa catheter sheath retraction device, suitable for connection to theproximal end of a stent delivery catheter (elongate body) for retractingthe catheter outer sheath, by virtue of a sheath retraction wire(elongate member), so as to expose a stent at the distal end of thecatheter. It will be appreciated, however, that the utility of thedisclosed device and the components of the actuator mechanism may findutility in alternative applications where actuation to achieve relativemotion between two elongate components is required.

In the present specification, as is usual in this technical field, theterm “proximal” refers to the direction or end of the device which, whenin use, is generally towards the medical practitioner, and the term“distal” refers to the opposite sense, i.e. towards the patient or awayfrom the medical practitioner.

The following description is made with reference to FIGS. 1 to 10generally, and with reference to specific ones of the figures, whereappropriate. The catheter sheath retraction device 1 generally includesa housing 10, a mover 20, a trigger 30, a pre-mover 40 and a limiter 50.

As shown in FIG. 1, the housing 10 is formed of a left housing 11, aright housing 12 and a lower housing 13, which together form an outershell of the catheter sheath retraction device 1. The housing componentswill typically be formed of any suitable surgically compatible materialto provide a substantially rigid outer shell. The housing is formed inan ergonomic shape, including ridged regions to provide grip for auser's hand. The housing is shaped so as to rest comfortably within onehand of a user, and to allow actuation of the trigger 30 with a singlehand by a user. The device is furthermore configured to be substantiallysymmetric along its longitudinal axis, to permit facile use with eitherhand. The left 11, right 12 and lower 13 housing components arepreferably molded separately before being joined together. The jointsmay be effected using suitable adhesive means, to form a sealed housingunit containing the components of the sheath retraction mechanismtherein. Preferably, the housing components 11, 12 and 13 are providedwith resilient male/female connecting portions, which allow the housingcomponents to be clipped together, as well as the joints being glued.

As is apparent from FIG. 2, the housing is provided with a rearconnector 15 and a front connector 16, by which to provide a fluid-tightconnection between the housing and a surgical catheter to be heldtherein. Connectors 15 and 16 preferably provide external access to theinternal fluid passageways of the surgical catheter, for example, so asto introduce flushing fluid into the catheter prior to use, and to allowinsertion and retraction of a guide wire through the catheter.

A conical nose or strain relief element 18 is provided at the distal endof the housing 10, to provide a rigid connection with the proximal endof a catheter. The strain relief element 18 enables the user to applycontrolled forces to the surgical catheter, and relieves localisedcompression and bending forces at the catheter proximal end where it isconnected to the housing 10. Front connector 16 and pusher 18 form thedistal hub by which a reinforcing member of the surgical catheter isheld in place relative to housing 10 to transfer compressive stresses tothe housing.

When a surgical catheter is connected to the catheter sheath retractiondevice 1, the connector 16 is configured to allow a sheath pull wire toextend distally into the housing from the catheter. The sheathretraction device 1 is provided with a mover 20 for retracting thesheath pull wire proximally into the housing 10.

As described in WO 2005/053574 A2, the sheath pull wire can be connectedto the sheath by, for example, first and second metal rings, one insidethe other, and sandwiching the sheath so that one of the metal rings isinside the sheath annulus and the other is outside the sheath annulus.The inside metal ring would normally be welded, soldered or brazed tothe distal end of the sheath pull wire (adhesives being generallydisfavored in failure-critical applications in such stent deliverydevices), while the outer metal ring can be swaged down onto the sheathto press the sheath onto the inner metal ring.

As best seen in FIG. 3, the mover 20 is provided with a mover reel 21,onto which the sheath pull wire is to be wound as the mover reel 21rotates. As can be seen, the mover reel 21 is formed with acircumferential V-shaped groove into which the sheath pull wire isreceived. The mover reel 21 is provided with slots or notches around itscircumference, into which an end connector of the sheath pull wire canbe received, to connect the sheath pull wire to the mover reel 21.

Although a sheath pull wire is mentioned as a specific, preferredexample of an elongate member by which to retract the catheter sheath,it is of course possible in alternative configurations to utilize aband, chain or other flexible member to connect the sheath to the mover20. As the mover reel 21 is rotated, the sheath pull wire is wound ontothe mover reel 21, in the V-shaped groove, thereby retracting the sheathand accumulating the sheath pull wire on the mover reel 21. Accordingly,as the sheath wire is refracted into the housing and wound on the moverreel 21, the sheath is retracted towards the catheter proximal end, asthe catheter itself is held in place by the housing 10 and strain reliefelement 18.

As shown in FIG. 3, in particular, the mover reel 21 is mounted on amover shaft 24 along with a number of further components. To enable themover shaft 24 to rotate in the center of the housing, it is mountedbetween a pair of left and right support frames 28 and 29, respectively.Holes are provided in support frames 28 and 29 to support the shaft 24,and to allow the shaft 24 to rotate substantially freely. Left and rightsupport frames 28 and 29, respectively, are configured to be fixedlymounted in the respective left and right housing portions 11 and 12.

As shown in FIG. 3, the mover reel 21 and mover shaft 24 are provided,on the left side of the catheter sheath retraction device 1, with amover toothed gear 22. Mover toothed gear 22 is rigidly coupled with themover reel 21, either via the mover shaft 24, or through beingconstructed as a unitary component therewith. In the present example, asshown in FIG. 10, the mover reel 21 and mover toothed gear 22 are formedas a unitary component, along with a limiter reel 53, to be describedfurther below. The mover reel 21 and toothed gear 22 are directlycoupled to the shaft 24, to rotate together therewith.

The mover shaft 24 is further provided with a trigger gear 26. As shownin FIG. 4, trigger gear 26 is not coupled directly to the mover shaft24, but is engaged therewith via a one-way clutch arrangement.Specifically, a one-way clutch 25 is provided on mover shaft 24. Clutch25 is a standard component for providing a rigid connection fortransmitting forces from the trigger gear 26 to the mover shaft 24 in adriving direction, and for allowing the trigger gear 26 to rotate freelyof the mover shaft 24 in the opposite direction.

As best seen in FIG. 10, for example, the trigger gear 26 is formed witha cylindrical through-hole 27 into which the one-way clutch 25 ispress-fitted. Grooves in the one-way clutch 25 outer surface deform theinner surface of through-hole 27 to fixedly engage the clutch 25 in thetrigger gear 26.

The one-way clutch 25 is configured to engage with mover shaft 24 so asto transmit drive from the trigger gear 26 to the mover shaft 24 in afirst, winding direction (anti-clockwise as shown in FIGS. 1, 2, 5, 7and 9 and clockwise as shown in FIGS. 6, 8 and 10). When rotated in thiswinding direction, the internal components of one-way clutch 25 engagemover shaft 24 to transmit drive from the trigger gear 26 to the movershaft 24. When the trigger gear 26 is rotated in the opposite sense, theinternal components of one-way clutch 25 are configured to disengagefrom mover shaft 24, allowing the trigger gear 26 to rotate separatelyfrom the mover shaft 24.

Accordingly, the trigger gear 26 may be rotated so as to cause the moverreel 21 to rotate in a first, winding direction, thereby to wind thesheath pull wire onto the mover reel 21. The trigger gear 26 will not,however, cause the mover reel 21 to rotate in the reverse direction,thereby unwinding the sheath pull wire from the mover reel 21.

Of course, in practice, the one-way clutch 25 is capable of transmittingsome torque to the mover shaft 24, even in the non-winding direction. Toprevent these unavoidable minimal forces from transmitting drive fromthe trigger gear 26 to the mover shaft 24 in the reverse direction, thecatheter sheath retraction device 1 is provided with a leaf spring 23,as shown in FIGS. 1 and 3. The leaf spring 23 is mounted to the housing10, in the present example to the left housing 11, to be rigidly andfixedly supported at one end thereof. The leaf spring 23 is mounted sothat the other, free end thereof is in contact with the teeth of themover toothed gear 22, and projects into the toothed region at an angleoblique to the radial direction of the toothed gear 22. By thisarrangement, the leaf spring 23 is configured to allow the toothed gear22 to rotate in a first direction (anti-clockwise, as shown in FIGS. 1,2, 5, 7 and 9), due to the teeth of the fixed gear 22 deflecting theresilient leaf spring 23 radially outwardly with respect to the toothedgear 22 so as to disengage it from the teeth as the toothed gear 22rotates.

As best seen in FIG. 9, however, when the toothed gear 22 attempts torotate in the opposite sense (clockwise, as shown in FIG. 9), theoblique interface of the free end of the leaf spring 23 with the teethof the toothed gear 22 causes the teeth of the toothed gear 22 to engagethe leaf spring 23 in a longitudinally compressive sense, rather than ina direction transverse to the leaf spring 23 long axis. Accordingly, theleaf spring 23 is not caused to deflect radially outwardly, and insteadengages positively with the teeth of the toothed gear 22, preventingrotation in the reverse, non-winding direction.

Accordingly, by the combined operation of the one-way clutch 25 and theratchet effect produced by the leaf spring 23, a drive system isconfigured for providing uni-directional drive in the winding directionof the mover reel 21 via the mover shaft 24. Furthermore, the degree ofrotation of the mover shaft 24 imparted by rotation of the trigger gear26 in the winding direction is not disturbed by subsequent reverserotation of the trigger gear 26, such as when the trigger 30 isreleased.

As shown in detail in FIGS. 6, 7 and 8, the catheter sheath retractiondevice 1 is provided with a trigger 30. Trigger 30 includes auser-engagement portion 33 which projects through an opening in thehousing 10 for engagement and manipulation by a user of the cathetersheath retraction device 1. The trigger 30 is pivotally mounted in thehousing 10 by a trigger pivot shaft 31, about which the trigger 30prescribes a part-circular, arcuate path. The trigger pivot shaft 31 maybe mounted in the housing 10 either in further holes provided in theleft and right support frames 28 and 29, or, as in the present example,directly mounted in a shaft receiving hole in each of the left and righthousings 11 and 12.

The trigger user engagement portion 33 is connected to a planetary gear32, which is also constrained to follow a part-circular arcuate path asthe trigger 30 is depressed by a user pressing on the trigger userengagement portion 33. The trigger 30 is mounted in the housing 10 sothat the planetary gear 32 engages with the trigger gear 26 mounted onthe mover shaft 24, as seen in FIGS. 3 and 8, for example. Accordingly,each depression of the trigger 30 rotates the trigger gear 26 in thewinding direction, so as to wind the mover reel 21 by a certain amount.The trigger 30 is also provided with a trigger spring 34 for biasing thetrigger from a fully depressed position to an extended position fullyprojected, within the trigger's arc of travel, from the housing 10.After the trigger 30 has been depressed from the extended position tothe depressed position, and then released, the spring 34 returns thetrigger 30 to the extended position through its biasing action. Althougha coil spring is specifically exemplified in the illustrated embodiment,any suitable biasing means may be used to return the trigger to theextended position after each depression. This trigger return motioncauses the trigger gear 26 to reverse in the opposite sense to thewinding direction. However, as noted above, no drive is transmitted tothe mover reel 21 in the unwinding direction, by virtue of the one-wayclutch 25. Again, as noted, any minimal forces attempting to rotate themover shaft in the unwinding direction are resisted by the leaf spring23 engaging with the teeth of the fixed gear 22.

In this way, a plurality of sequential depressions of the trigger 30 canbe used to fully retract the catheter sheath by winding the sheath pullwire on the mover reel 21. Each full depression of the trigger 30 willretract the sheath pull wire by a substantially constant pre-determinedamount. Within practical limits, the trigger 30 can be utilized to windup a sheath pull wire of substantially any length, unconstrained by thephysical length of the housing 10. Accordingly, the same housing 10 andretraction mechanism, comprising the mover 20 and trigger 30, can beutilized to retract a catheter sheath by substantially any given length,without needing to modify the components of the housing 10, mover 20 ortrigger 30.

The distance by which any sheath must be retracted is essentially thesame as the length of the stent to be deployed, typically 20 mm to 200mm. The sheath may run along substantially the entire length of thecatheter, which would have a typical length from 60 cm to 135 cm,although catheter lengths up to 200 cm are also known, for endoscopicapplications and such like. Alternative sheath designs include a sheathonly along the distal portion of the catheter delivery system, in whichcase the length of such a sheath would normally be from 100 mm to 400mm, suitable for use with the existing standard lengths of stents to bedeployed.

On the other hand, it is preferable for the operator of the cathetersheath retraction device to have an indication of when the sheath at thedistal portion of the catheter has been fully retracted, such that astent mounted at the distal end of the catheter has been released. Tothis end, a limiter 50 is provided. Limiter 50 is mounted, in thepresent example, in a proximal portion of the housing 10. The limiterincludes a tethered line, which is realized in this example by a spool51 on which a band 52 is wound. In a preferred embodiment, the limiterband 52 is provided of a fixed length, with reference markings toindicate particular positions along the band 52 which each denote anamount by which the band 52 is to be unwound (and rolled-up onto limiterreel 53). The amount provided by each marker provides for a consumablelength of the band 52 remaining spooled on the limiter spool 51 whichcorresponds to (but is not necessarily equal to) the distance by which aparticular sheath to be retracted by the catheter sheath retractiondevice 1 is to be retracted. During manufacture or set-up of thecatheter sheath retraction device 1, the band 52 is unspoiled from spool51 and around onto limiter reel 53 until the marker corresponding to therequired sheath retraction distance is revealed, leaving the spooledportion of band 52 with a remaining consumable length corresponding tosaid required sheath retraction distance.

In practice, there are twelve standard lengths of stent (there aretwelve stent lengths commonly adopted within the medical devicesindustry, as an informal standard, ranging from 20 mm to 200 mm).Accordingly, each band 52 may be provided with eleven or twelve suchmarkers, allowing accurate adjustment of the band 52 consumable lengthto any one of the twelve standard lengths. Stents up to 300 mm in lengthare also contemplated, and bands of appropriate length having any numberof suitable markers may of course be provided to accommodate any suchother stent length. Most preferably, the adjustment of the band 52consumable length is undertaken during manufacture and assembly of thecatheter sheath retraction device 52. As an alternative, a specificlimiter band 52 may be selected which has a particular length, inparticular including a consumable portion having a length corresponding(but not necessarily equal) to the distance by which a particular sheathis to be retracted by the catheter sheath retraction device 1.

The unspooled free end of the limiter band 52 is provided with aconnector, such as a ball or cylinder welded or otherwise joined ontothe end of the band 52, for example. The band 52 is substantiallyinextensible in its lengthwise direction. The free end of the limiterband 52 provided with the connector is attached to the limiter reel 53,which is provided in the present example mounted on the shaft 24 betweenthe mover reel 21 and the toothed gear 22.

As visible in FIGS. 3, 4, 6, 7, 8 and 10, the limiter reel 53 isprovided with one or more female connector portions around itscircumference, into which the connector on the free end of the limiterband 52 may be inserted and retained. Preferably, the limiter reel 53 isprovided with plural female connector portions, which enable the freeend of the limiter band 52 to be attached at a variety of positionsaround the limiter reel. This enables the mover reel 21 to be rotated toa suitable initial position in dependence on the initial winding-on ofthe sheath pull wire onto the mover reel 21, and for connecting thelimiter band to the limiter reel to provide the correct consumablelength independently of the rotational position of the mover reel 21.The length of the limiter band to be consumed can therefore be adjustedwith greater freedom, unconstrained by the position of the sheath pullwire.

In operation of the catheter sheath retraction device, as the movershaft 24 rotates to wind the sheath pull wire onto the mover reel 21,the limiter band 52 is similarly wound onto the limiter reel 53, as itis unspooled from the spool 51. When the pre-determined length of thelimiter band 52 has been unspooled from the spool 51 and wound on thelimiter reel 53, the inextensible limiter band 52 prevents furtherrotation of the limiter reel 53, and consequently prevents furtherrotation of the mover shaft 24 and mover reel 21. This indicates to theuser that the catheter sheath retraction device 1 has fully retractedthe catheter sheath.

Accordingly, by simply adjusting the consumable length of limiter band52 during manufacture or set-up of the retraction device, or bysubstituting the limiter band 52, according to the length of sheath tobe refracted, the further components of the catheter sheath retractiondevice 1 can be left unaltered, regardless of the length of the cathetersheath to be retracted, thereby rendering identical (or virtuallyidentical) ones of the device applicable to numerous sheath withdrawalapplications with only this minor modification.

Turning now to FIG. 9, in particular, a pre-mover 40 of the cathetersheath retraction device 1 will be described. The pre-mover 40 ispreferably a separate and distinct mechanism from any actuator device,such as trigger 30, for effecting retraction of the sheath, and isdissimilar in operation from incremental or bulk retraction actuatorsknown in the prior art.

The illustrated pre-mover 40 includes a slider arm 43 provided with aslider arm groove 44 extending partially along the length thereof.Slider groove 44 is mounted on a slider pin 47 provided in the housing10. Slider pin 47 may be formed as part of the left housing 11, or mayform part of the left support frame 28. Slider arm 43 is thusconstrained to move so that the slider groove 44 travels along sliderpin 47.

The slider arm 43 is provided at its proximal end with a pre-mover rackgear 45. Rack gear 45 is configured to engage with the mover toothedgear 22, so that movements of the slider arm 43 in the proximaldirection (in the right-hand direction as shown in FIG. 9) will causethe rack gear 45 to rotate the toothed gear 22 in the winding direction(anticlockwise in FIG. 9).

The pre-mover 40 is provided at the distal end with a pre-mover fingerbutton 41, which is mounted on a pre-mover button slider 42. Thepre-mover button slider 42 is pivotally connected to the distal end ofthe slider arm 43, mounted on a pivot shaft 46 of the slider arm 43 (seeFIG. 6).

The pre-mover button slider 42 is mounted in a track provided in thehousing 10, as shown in FIGS. 1 and 2. The button slider 42 is slidablealong the track in the housing between a distal, locking position and aproximal release position. The pre-mover finger button 41 is configuredto project outside the housing 10 when the button slider 42 is mountedin the track of the housing, as shown in FIG. 2, to enable manipulationby a user of the catheter sheath retraction device 1. The finger button41 is configured for retraction by a user's single digit in the proximaldirection.

As visible in FIG. 1, notches or dimples may be provided along the trackin which the button slider 42 is mounted. In particular, a first notch,or pair of notches, is provided near to the distal end of the track anda second notch, or pair of notches, is provided near to the proximal endof the track. These notches provide a tactile indication to a user ofthe catheter sheath retraction device 1 to indicate, firstly, when theslider button has been retracted from the distal locking position so asto effect initial release of the button slider 42 from the lockingposition, and, secondly, when the slider button 42 has been fullyretracted.

With the button slider 42 in the distal locking position, the pre-moverrack gear 45 is engaged with the teeth of the toothed gear 22 of themover 20. The inclination of the track along which the button slider 42can travel, in combination with the provision of the distal notches inthe slider track, means that, with the pre-mover in the lockingposition, slider arm 43 is immobilized so that the toothed gear 22 issubstantially locked against rotation due to the pre-mover rack gear 45holding the toothed gear 22 stationary. Accordingly, the pre-mover 40functions as a locking device to prevent premature unintentionaldepression of the trigger 30 and consequential retraction of the sheathpull wire through rotation of the mover reel 21.

The pre-mover finger button 41 may readily be used, however, due to itsdifferent alignment to slider arm 43, to proximally retract the buttonslider 42 along the track provided in the housing, thereby causingslider arm 43 to move proximally, with groove 44 tracing along thepre-mover slider pin 47. This causes the rack gear 45 to rotate thetoothed gear 22, at the same time rotating the mover shaft 24 and moverreel 21, in the winding direction.

The track along which button slider 42 is configured to run, and thepre-mover rack gear 45, both have a short fixed length. When the fingerbutton 41 has been retracted to the proximal release position, the slidearm 43 has been displaced proximally to a position in which the rackgear 45 is disposed entirely proximally of the toothed gear 22, and isdisengaged therefrom, allowing the toothed gear 22 and mover shaft 24thereafter to rotate freely of the rack gear 45. (In alternativeembodiments where the pre-mover is not implemented by a linear slider,other means may be provided by which to disengage the pre-movementmechanism from the toothed gear 22 or equivalent component. For example,were a pivotally-mounted rack gear to be used, the rack gear might bedisengaged by being pivoted downwardly out of mesh with the toothed gear22 teeth, or in other arrangements might be displaced out of mesh bymoving the rack and toothed gear along the toothed gear 22 axis relativeto each other.)

The pre-mover 40 is provided in order to effect a small pre-determinedrotation of the toothed gear 22 in the winding direction, preferablywithout effecting any notable retraction or peeling at the sheath distalend or tip. The purpose of the pre-mover 40 is not to effect any bulkmovement or retraction of the catheter sheath by winding any substantialportion of the sheath pull wire onto the mover reel 21. Instead, thepre-mover 40 is configured to effect a pre-movement adjustment of thepull wire and catheter sheath relative to the catheter, in preparationfor retraction of the sheath using the trigger 30. This adjustment ofthe sheath pull wire by pre-winding the mover reel 21 by apre-determined small amount has two effects. Firstly, the initialmovement can take up any slack in the sheath pull wire which may haveresulted from, or is provided to allow, the flexible bending movementswhich the catheter undertakes when being folded or inserted into abodily lumen. Accordingly, any slack in the sheath pull wire is taken upto ensure a taut direct connection between the mover reel 21 and thecatheter sheath to be retracted. Secondly, the pre-movement adjustmentcan further function to pre-tension the catheter, by pre-tensioning thepull wire and the catheter sheath at the distal portion of the catheter,thereby producing a corresponding compressive force along the catheterlength, so as to reduce any remaining compressive flexibility along thecatheter length. This serves to pre-tension the retraction mechanism,with the sheath pull wire being pulled taut between the sheath and themover reel 21. With the sheath pull wire pre-tensioned, and with thepre-mover in the proximal release position, the leaf spring 23 functionsto prevent motion of the mover reel 21 in the unwinding direction (dueto tension in the pull wire), and to maintain the sheath and pull wirein the adjusted pre-tensioned state.

Accordingly, by providing the pre-mover 40, a preliminary adjustment ofthe sheath pull wire can be effected, to prepare the catheter for sheathretraction. This ensures that subsequent actuation of the trigger 30will result in a direct corresponding motion of the sheath, as the moverreel 21 winds the sheath pull wire to proximally retract the cathetersheath. This direct pre-tensioned condition provides greater tactilefeel for a medical practitioner using the catheter sheath retractiondevice 1, and improves the accuracy by which the stent being released atthe distal end of the device can be positioned and released at thetreatment site. The pre-mover 40 further functions to operate as alocking device, securing the retraction mechanism of the catheter sheathretraction device 1 against accidental, premature retraction of thesheath pull wire, such as during transport and during insertion of thecatheter into a patient.

From the foregoing, it will be appreciated that the pre-movementadjustment is effected to prepare the stent delivery device providedwith such a catheter sheath retraction device for bulk sheath withdrawaland stent release. Although in an ideal configuration the pre-movementadjustment would not cause the catheter sheath to be retracted relativeto the catheter, in practice some retraction of the sheath may occur,even to the extent that the stent extreme distal end may become exposedat the catheter distal end portion.

This is to be contrasted, however, with the arrangement in two-stagecatheter sheath retraction systems. In such systems, the catheter sheathis firstly partially withdrawn, part way along the stent, using anactuator with a high mechanical advantage so as to effect a controlledwithdrawal at a slow rate. By this process, the stent distal end isgradually released from the catheter sheath to expand into contact withthe wall of the bodily lumen into which the stent is being implanted,allowing the stent distal end to be positioned at the treatment locationwith high precision. When the stent distal end has been positioned, thecatheter sheath is then secondly withdrawn the remaining distance tofully release the stent, using an actuator with a low mechanicaladvantage to effect sheath withdrawal at a fast rate. This ensures thatonce the stent distal end is positioned the stent can be quickly fullyreleased, to reduce the chances of inadvertently causing trauma to thepatient through relative movement between the stent and the vessel wallafter the stent distal end is engaged with the bodily lumen.

With the pre-movement adjustment presently provided, any sheathretraction is preferably insufficient to expose the stent distal endportion from beneath the sheath. Even if the stent extreme distal endportion is partially exposed, the degree of exposure will beinsufficient to allow the stent to expand into circumferentialengagement with the wall of the bodily lumen into which the stent is tobe implanted. In terms of the stent diameter, the stent is preferablyexposed during pre-movement adjustment only by an amount permittingradial expansion by up to 10% or less of the delivery diameter of thestent, more preferably by up to only 5% or less. For typical catheterand stent dimensions, the pre-movement adjustment will represent amaximum sheath withdrawal of 5 mm to 10 mm at the distal end.

Although a specific example of a catheter sheath retraction device 1 hasbeen described and illustrated, it will be appreciated that numerousmodifications may be effected based upon the same operational principlesby which the described device functions.

For example, the pre-mover 40 may be provided by alternative means foradjusting the sheath pull wire prior to bulk retraction of the sheathrelative to the catheter, other than by using a slider arm 43 and rackgear 45. Even if a rack gear based mechanism is utilized, the slider armneed not be configured to provide a secure locking function, andalternative locking devices may be utilized. Similarly, the pre-moverbutton could be mounted at the proximal end of the catheter sheathretraction device, to adjust the mover 20 by a proximal pullingretraction, rather than a proximal pushing retraction of the rack gear45. Numerous further alternatives are clearly possible.

Similarly, the advantages achieved by the pre-mover 40 are notrestricted to embodiments utilizing a trigger 30 for actuating the moverreel 20 to retract the sheath pull wire. Various actuation mechanismsutilizing thumb wheels, knobs, triggers and sliders are known forretracting a sheath pull wire, of which the skilled reader will be fullyaware.

A number of published documents have been mentioned above. Many of theseare from the present proprietor, and represent steps along the way tothe present invention. It is intended that the disclosures of thesementioned earlier documents are incorporated by reference in theirentirety into the teaching and disclosure of the present specification,as if each individual publication or patent application werespecifically and individually put forth herein.

What is claimed is:
 1. A device comprising: a reel that rotates andwinds up a wound length of an elongate member; and a limiter that limitsreel rotation after the reel winds up the wound length, wherein: thelimiter comprises a tether connected to the reel through a lineconnector, the reel winds up the tether until, when taut, the tetherprevents further rotation, the tether has a total length greater than aconsumable length and the consumable length corresponds to the woundlength, and the tether has reference markings indicating differentconsumable lengths corresponding to different wound lengths, theconsumable lengths set by consuming the tether up to the referencemarkings indicating an amount of remaining consumable length, whichcorresponds to the wound length.
 2. The device of claim 1, wherein thetether is wound on a spool and reel rotation winds the tether from thespool onto the reel.
 3. The device of claim 2, wherein the devicefurther comprises a sheath disposed around a stent, and wherein theelongate member is a sheath retraction wire connected to the sheath. 4.A surgical apparatus including the device of claim 3, comprising ahousing and a mover connected to a catheter.
 5. The surgical apparatusof claim 4, wherein the stent is releasably disposed on the catheter,and wherein the stent is released by moving the sheath retraction wirerespective to the catheter.
 6. The surgical apparatus of claim 5,wherein: the stent is a self-expanding stent, the device is configuredfor a pre-movement adjustment of the sheath retraction wire relative tothe catheter, and the pre-movement adjustment is insufficient to releaseany part of the stent to an expanded diameter exceeding 110% of anunexpanded stent diameter.
 7. The surgical apparatus of claim 6, whereinthe pre-movement adjustment is insufficient to release any part of thestent.
 8. The device of claim 1, further comprising a sheath disposedaround a stent, wherein: the elongate member is a sheath retraction wireconnected to the sheath that retracts the sheath as the reel winds upthe sheath retraction wire, and the device limits retraction of thesheath using the limiter that limits a wound length of the sheathretraction wire to the consumable length.